1. Field of the Invention
The present invention relates to the gradual replacement of ozone-damaging Freon 12(copyright) refrigerant with a refrigerant that is less damaging to the ozone layer in systems designed to use Freon 12(copyright). More particularly the present invention relates to an improved refrigerant composition, method and apparatus for refrigeration wherein two non-Freon 12 refrigerants are mixed in a defined ratio such that the temperature-pressure relationship of the mix approximates that of ozone-damaging Freon 12(copyright), especially at high operating temperatures. The mixture is compatible with Freon 12(copyright) so that it can be added to supplement and gradually replace ozone-damaging Freon 12(copyright). A further particularity of the instant invention relates to an improved method and apparatus for refrigeration wherein refrigerant mixture is mixed with a soluble lubricating oil to provide lubrication to the apparatus. The lubricant is soluble in both the mixture of the invention and Freon 12(copyright) refrigerant.
2. General Background
Until recently, R-12 or dichlorodifluoromethane ((hereinafter sometimes called xe2x80x9cFreon 12(copyright)xe2x80x9d); while Freon 12(copyright) is a trademark of E. I. du Pont de Nemours and Co. Inc. for dichlorodifluoromethane, hereinafter xe2x80x9cFreon 12(copyright)xe2x80x9d is used in this specification to denote dichlorodifluoromethane, regardless of the source) was the major, if not sole refrigerant, used in automobile air-conditioners, refrigerators, freezers and window air-conditioning units. Recently, however, Freon 12(copyright) has come under attack both nationally and internationally as an ozone layer-damaging chemical. In recent years, both the national and international scientific communities have linked Freon 12(copyright) with damage to the earth""s protective ozone layer. Automobile air-conditioners, refrigerator/freezers and window air-conditioning units are believed to be a significant global source of ozone-damaging Freon 12(copyright).
In response to both scientific concern and a national and global outcry over the use of Freon 12(copyright) in air-conditioning, the United States Congress has acted to first reduce and then ban the use of Freon 12(copyright) in air-conditioning units.
One of the first areas in which the use of Freon 12(copyright) is to be phased out is in automobile air-conditioning. As a first step toward phasing out the use of Freon 12(copyright) in automobile air-conditioning units, Congress is phasing out the use of Freon 12(copyright) in new automobiles and has banned the sale of Freon 12(copyright) in small retail quantities for the do-it-yourself air-conditioner recharger market.
However, at the time of this application, the vast majority of automobiles in use in the United States contain Freon 12(copyright)-based air-conditioning units, and approximately 40% of new automobiles continue to contain Freon 12(copyright)-based air conditioners.
Prior to banning the retail sale of small quantities of Freon 12(copyright), owners of automobiles with Freon 12(copyright)-based air-conditioning units were able to recharge, or xe2x80x9ctop-offxe2x80x9d the level of coolant in their automobile air-conditioners without the need for expensive professional service. Millions of units of Freon 12(copyright) recharging units were sold in the United States prior to being banned in January, 1994.
These Freon 12(copyright) recharger kits typically consisted of a 12 ounce (0.36 liter) aerosol can containing Freon 12(copyright). The cans were fitted with an aerosol dispensing outlet that was compatible with a commercially available refrigeration manifold. In order to recharge an air-conditioning system, a customer needed to only fit the can to the manifold and discharge, or xe2x80x9cdrop inxe2x80x9d the can""s refrigerant charge directly into the air conditioning system, thus eliminating the need to bleed the system of existing Freon 12(copyright) before recharging.
Following Congress""s ban on the retail sale of Freon 12(copyright) recharger kits, millions of automobile owners with Freon 12(copyright)-based air-conditioning units were left with no choice other than to seek expensive professional service to recharge their automotive air-conditioning units.
Also in response to Congress""s ban on the use of Freon 12(copyright) in automobile air-conditioning, professional automotive service dealers began to retrofit existing Freon 12(copyright)-based air-conditioning units into new, non-Freon 12 refrigerant-compatible units.
The refrigerant authorized by the Environmental Protection Agency (EPA) to replace Freon 12(copyright) in automobile air conditioners is 1,1,1,2-tetrafluoroethane (hereinafter sometimes referred to as xe2x80x9c134axe2x80x9d or xe2x80x9ctetrafluoroethanexe2x80x9d). Unfortunately, 134a has a markedly different temperature-pressure relationship at high operating temperatures than does Freon 12(copyright).
Because of this difference in the temperature-pressure relationship of Freon 12(copyright) and replacement 134a, existing Freon 12(copyright)-based systems cannot simply be bled of Freon 12(copyright) and refilled with 134a. Were Freon 12(copyright) to be replaced by 134a in a non-retrofitted Freon 12(copyright)-based air-conditioning unit, the unit could not be operated at high temperatures because the significantly higher pressure of 134a over Freon 12(copyright) would damage the unit. Hence, non-retrofitted, Freon 12(copyright)-based units that are simply refilled with replacement 134a are inoperative at high operating temperatures; thus, inoperative at precisely the time that air-conditioning is most desired.
Further, simply mixing 134a with existing Freon 12(copyright) in order to replenish, or xe2x80x9ctop offxe2x80x9d the level of coolant is not feasible. When 134a is mixed with Freon 12(copyright), the mixture takes on the pressure characteristics of a higher pressure azeotrope, as opposed to Freon 12(copyright). The temperature-pressure profile of 134a becomes markedly different from that of Freon 12(copyright) at temperatures within the high end of the normal refrigerant operating temperature range. Hence, replenishing lost Freon 12(copyright) with 134a in a Freon 12(copyright)-based air-conditioning system would lead to the same problems as the use of pure 134a in a non-retrofitted Freon 12(copyright)-based system: damage to the system caused by 134a""s high pressure at high operating temperatures.
In addition, 134a is insoluble with the lubricant used in existing, non-retrofit Freon 12(copyright)-based systems. Thus, mixing 134a with Freon 12(copyright) in a non-retrofit Freon 12(copyright)-based unit leads to loss of lubrication and subsequent damage to the system.
Hence, in the absence of Freon 12(copyright) recharger kits, owners of automobiles with Freon 12(copyright)-based air conditioners face but one choice when the level of their air-conditioning coolant was low: professional servicexe2x80x94at a significant costxe2x80x94to remove the existing Freon 12(copyright), and retrofit the system to be compatible with 134a gas.
Prior to January 1994, owners of the millions of automobiles with Freon 12(copyright)-based air-conditioning units had a choice of whether to merely top off the level of air-conditioning coolant with an inexpensive do-it-yourself Freon 12(copyright) recharger kit or to undergo an expensive retro-fitting process. However, at the time of this application, owners of automobiles with Freon 12(copyright)-based air-conditioners no longer have this choice. They must undergo expensive professional maintenance, or discontinue the use and enjoyment of their automobile air-conditioners.
Thomas et al. (U.S. Pat. No. 5,254,280) discloses a lubricant developed for use with 134a and the combination of that lubricant with a refrigerant which is a replacement for R12. The lubricant contains polyoxyalkylene glycol, which is hydrophilic and will damage the system as discussed below.
Tamura et al. (U.S. Pat. No. 4,983,312) discloses a refrigerant blend similar to that claimed herein, but without a lubricant; it cannot be used in R12 automobile air conditioning systems, for the reason discussed below.
Systems that contain R12 are rarely produced today. New auto air conditioners use Refrigerant 134a. One sees R12 in older systems. These older systems have common components: R12, R12 mineral oil lubricant, and water that is sequestered into the dryer. If 134a were added to the system, it would damage the system as follows: (1) if no lubricant is added to the 134a (as in Tamura et al.), then the R12 system would be starved for lubricant, since the 134a gas is not miscible with the mineral oil lubricant; (2) if a synthetic lubricant is added to the 134a (as in Thomas et al.), then there is a different problemxe2x80x94that of moisture. Older systems have water trapped in their dryers. The synthetic lubricants (such as polyglycol- or polysiloxane-based lubricants) are hydrophilic. Thus, they are not only miscible with R12 and 134a, they are also partially or completely miscible with water. Thus, if they are introduced into an R12 system, they will pull this water out of the dryer into the refrigerant flow, initiating corrosion and damage to pressure switches and the TX valve. This is why Elf Atochem and DuPont publish elaborate flushing procedures and high efficiency dryer changeouts to prevent damage to the cooling system. There is also some concern with the compatibility of residual chlorine-bearing compounds on the 134a/blend lubricants (synthetic polyglycols and polysiloxanes).
Residual R12 vapors (CFC""s) mixed with water yield hydrochloric acid fumes and hydrofluoric acid fumes. The dryer in a normal R12 air conditioning system contains a molecular sieve to trap moisture.
Wilczek, Gorski, and Anton of DuPont have patents on synthetic lubricants in various 134a and 134a/125 refrigerant systems. The DuPont patents discuss a gas known as 125 (pentafluorethane). 125 is five fluorine atoms bonded to an ethane molecule. This is a very large molecule for a refrigerant. It is not currently being produced, except as laboratory samples. Due to the nature of the molecular structure, the present inventor believes that the blend of 134a/125 will fractionate upon release to the atmosphere, as with a system leak. This fractionation will change the percentage composition of the blend and preclude its use in an automotive air-conditioning system where leaks are common.
The invention provides a method and apparatus that are environmentally sound alternatives to the use of Freon 12(copyright) as a refrigerant. More particularly, the invention provides a mixture of at least two refrigerants that are miscible with each other, and compatible with Freon 12(copyright) while at the same time possessing a temperature-pressure profile that approximates that of Freon 12(copyright) over the operating range of ambient temperatures usually encountered by air conditioning units or other apparatus utilizing Freon 12(copyright) as a refrigerant. The invention also provides a lubricant, that is compatible with both the environmentally sound refrigerant of the invention and with Freon 12(copyright), so that mixtures of the refrigerant according to the invention and Freon 12(copyright) may be utilized with this lubricant in the refrigeration systems without deleterious effect upon moving parts of the refrigerating apparatus that require lubrication from the refrigerant.
More particularly, the invention provides a mixture of chlorodifluoroethane and tetrafluoroethane in specific proportions that provide a temperature-pressure relationship that approximates that of Freon 12(copyright) over the range of ambient temperature operating conditions in which Freon 12(copyright) is a useful refrigerant. More specifically, the refrigerant according to the invention comprises from about 15 to about 40 weight percent chlorodifluoroethane and from about 85 to about 60 percent tetrafluoroethane, based upon the total weight of chlorodifluoroethane and tetrafluoroethane. Preferably, the refrigerant includes from about 15 to about 20 weight percent chlorodifluoroethane and from about 85 to about 80 weight percent tetrafluoroethane. Most preferably, the refrigerant includes about 20 weight percent chlorodifluoroethane and about 80 weight percent tetrafluoroethane. In addition, the refrigerant according to the invention also includes from about 0.5 to about 2 weight percent (based on the weight of chlorodifluoroethane and tetrafluoroethane) of a lubricating oil that is soluble in dichlorodifluoromethane, chlorodifluoroethane, and tetrafluoroethane. Preferably, the lubricant is selected from those lubricants sold by Royal Lubricants Company under the trademarks ROYCO(copyright) 783C or ROYCO(copyright) 783D. It should be understood, however, that other lubricating oils may also be used, as long as they are compatible with chlorodifluoroethane, tetrafluoroethane, and Freon 12(copyright).
ROYCO(copyright) 783C and ROYCO(copyright) 783D are trademarks of Royal Lubricants Company Inc., E. Handover, N.J., for lubricants having the following composition:
60-80% hydrotreated light naphthenic distillate,
10-20% acrylic polymer in severely hydrotreated mineral oil,
5-15% solvent refined light naphthenic distillate petroleum,
2-7% additive containing barium dinonylnaphthalenesulfonate,
 less than 0.5% butylated triphenyl phosphate, and
 less than 2% minor additive.
While it is intended that the substitute refrigerant according to the invention may be utilized to replace lost Freon 12(copyright) that has escaped from apparatus, the substitute refrigerant of the invention may also be utilized to completely refill apparatus that have been designed for use with Freon 12(copyright), since the refrigerant has a temperature-pressure profile that closely approximates that of Freon 12(copyright). Thus, when the refrigerant is used as a complete replacement for Freon 12(copyright), it is no longer necessary that the lubricant be compatible with dichlorodifluoromethane but only that it should be compatible with tetrafluoroethane and chlorodifluoroethane.
Further, whereas the substitute refrigerant of the invention is less damaging to the ozone layer than Freon 12(copyright) is useful in air conditioning units, and in particular automobile air conditioning units, it is not so limited in its use. Indeed, the refrigerant may be utilized as a substitute or replacement for Freon 12(copyright) in virtually any application, thereby eliminating the use of ozone layer-damaging Freon 12(copyright).
In further specifics, the invention provides a canister containing a mixture of tetrafluoroethane and chlorodifluoroethane that may be fitted with an outlet manifold that is compatible with a Freon 12(copyright) recharging manifold that is typically used to recharge an apparatus with the latter refrigerant. Refrigerant may then be allowed to flow from the container through the manifold and into the apparatus to replace Freon 12(copyright) refrigerant that has been lost from the refrigeration system or to completely fill the apparatus.
When mixing the components of the refrigerant blend of the present invention, one should first mix the lubricant with refrigerant 142b, then mix that mixture with refrigerant 134a; otherwise, the product does not mix properly.
The lubricant preferably has a viscosity of 5 to 500 centistokes, more preferably 5 to 100 centistokes, even more preferably 5 to 50 centistokes, and most preferably 5 to 10 centistokes. The lubricant having a viscosity of 5 to 10 centistokes is preferred because it is fluid enough to get to the seals in mobile air-conditioning systems and can stop leaks.
The percentage by weight of lubricant in the refrigerant blend is preferably 0.5-2%, more preferably 1-2%, even more preferably 1.25-2%, and most preferably 1.5-1.75%. The percentage by weight of lubricant in the refrigerant blend is for example 1.75xc2x10.05%.
The preferred lubricant is severely hydrotreated naphthenic/paraffinic lubricant, such as ROYCO(copyright) 783C and ROYCO(copyright) 783D or Alox 1680. Other possible lubricants are Sunpar 2280, Lubrizol 403, Sunthene 200, or Alox 1680 naphthenic lubricant. Mobil One 5-weight naphthenic/paraffinic synthetic motor oil (it is hydrophobic) could work as a lubricant, but it is relatively expensive.
It is preferable to include a corrosion inhibitor (otherwise corrosion will probably occur within 6 months). The corrosion inhibitor is preferably one for anhydrous systems (such corrosion inhibitors comprise calcium, barium, or phosphated salts). The corrosion inhibitor can be bonded to the lubricant.
Preferably no more than 5% by weight of the lubricant is hydrophilic lubricant (some aliphatic hydrocarbon solvents can absorb up to 5% by weight water and still maintain lubricating integrity). More preferably, no more than 2% by weight of the lubricant is hydrophilic lubricant. Most preferably, the refrigerant blend contains no hydrophilic lubricant.
In order for the parts of the refrigerant system to function properly, 4-5% of total weight of refrigerant must be lubricant. When adding the refrigerant blend to a refrigerant system, one should leave the lubricant in the system if one for some reason takes out the Freon 12.
The lubricant is preferably hydrophobic (immiscible with water).
The present invention was designed to be utilized as a direct R12 replacement in automobile refrigeration systems. It was designed as a true replacement, in which no modifications or parts are used to adapt the system for the refrigerant of the present invention.
The naphthenic, mineral oil based lubricant system of the claimed invention is miscible with the 134a/142b blend and with R12. This allows for mixing of residual R12 and the refrigerant of the present invention, without the release of residual water in the dryer and subsequent system damage (as will happen if the synthetic lubricants disclosed in Thomas et al. and the DuPont patents are used).
The present invention can be used as a drop-in replacement for R12, without retrofitting the automobile air conditioning system or flushing it out.
The present invention provides a mixture of non-Freon 12 refrigerants that are less damaging to the Earth""s ozone layer and that are approved by the U.S. Environmental Protection Agency for use in air-conditioners. The invention mixture is compatible with Freon 12(copyright) and can be used to fill or xe2x80x9ctop offxe2x80x9d existing Freon 12(copyright)-based refrigeration systems. It is expected that the present invention will gradually replace Freon 12(copyright) in Freon 12(copyright)-based air-cooling systems, without the need to remove Freon 12(copyright) from existing systems and without the need to retrofit existing Freon 12(copyright)-based systems for non-Freon 12 replacement refrigerants.
Specifically, the preferred embodiment includes a mixture of 142b and 134a refrigerants and a compatible lubricant such as ROYCO(copyright) 783C or 783D, provided under pressure in an aerosol can equipped with an outlet compatible with existing Freon 12(copyright) recharger kit manifolds, so that the can""s refrigerant and lubricant mixture can be added on top of existing Freon 12(copyright) coolant in Freon 12(copyright)-based coolant systems. Also, the invention provides the possibility of using new refrigerant systems, originally designed for xe2x80x9cFreon 12(copyright),xe2x80x9d by supplying an EPA-approved refrigerant so that retrofitting for 134a use is not required.
In the most preferred embodiment, the invention provides an aerosol can like the standard 12 ounce (0.36 liter) can formerly used for containing xe2x80x9cFreon 12(copyright),xe2x80x9d but containing about 80% by weight 134a and about 20% by weight 142b. The can also contains the preferred lubricant, ROYCO(copyright) 783C or 783D in solution with the coolant mixture at a percent by weight of between 0.5% and 2%.
Existing Freon 12(copyright)-based air-conditioning systems use a small amount of a vegetable or hydrocarbon oil to lubricate the compressor. This oil has a very low vapor pressure, and is not soluble with either pure 134a or the 80/20% wt/wt mixture of 134a and 142b. Hence, adding 134a to replace Freon 12(copyright) in existing Freon 12(copyright)-based air-conditioning systems leads to compressor breakdown from lack of sufficient lubrication. The invention provides lubricants that are compatible with the invention mixture of 134a and 142b, and with xe2x80x9cFreon 12(copyright),xe2x80x9d and that are suitable for lubricating refrigerant compressors and other air-conditioner component parts. The most preferred ROYCO(copyright) 783C or 783D lubricants, on the other hand, are soluble in a 134a/142b mixture. This solubility allows the replacement refrigerant blend to lubricate the air-conditioning system, preventing damage to the compressor and component parts of the system.